EFFECTIVENESS OF INJECTING PURE OXYGEN INTO SEALED COLUMNS FOR IMPROVING WATER-QUALITY IN AQUACULTURE

Sealed columns are simple, effective devices for economically adding oxygen to water and have considerable potential for use in aquaculture. Increasing the oxygen content of water enables fish culturists to increase fish loads and improve the rearing environment. We conducted tests to evaluate the effectiveness of pure oxygen injected into sealed columns to increase dissolved oxygen (DO) levels in waters at four hatcheries. Nominal water flows of 770, 481, 385, and 288 gal/min were evaluated at gas-to-liquid ratios of 0.5, 1.0, 2.0, 3.0, and 4.0%. Delta DO (amount of oxygen added to the water) ranged from 6 to 28 ppm as gas-to-liquid ratios increased from 0.5 to 5.3. Tests also indicated that there were no differences in performance of a column with 3 ft of packing versus 5 ft of packing at the flows tested. Two types of packing were compared, but little difference between them was observed. Operation of one column with packing and one equipped with a spray nozzle without packing yielded similar results; the column with the nozzle performed as well as the column with packing at the higher water flows.